Radiofrequency cavities (radiofrequency resonators) are used, for example, in particle accelerators for accelerating electrically charged particles. In order to excite a radiofrequency electromagnetic oscillation in such an RF cavity, the RF cavity must be supplied with RF power. It is known to generate RF power, for example, by means of a tetrode or a klystron, at a first position and then deliver it via a waveguide to the RF cavity arranged at a second position. The waveguide may, for example, be connected to the RF cavity via an opening or by inductive coupling. The various injection points must be accurately matched to one another. Nevertheless, each injection point is associated with inevitable power losses.